The present invention relates to a device for coating small solid particles with a solidifying layer derived from a liquid, where the solid particles and the liquid are supplied axially from one side into a rotating disk-like turbine that is set into rotation via a drive shaft projecting from the side opposite the supply side.
Devices of this type have been known, for example, from EP 0 048 312 A1. In the case of these arrangements, the liquid content, normally formed by the melt of a material that is solid at room temperature, is fed into the system from above through a pipe extending along the axis of the turbine. The solid particles are fed onto the rotating disk via a hopper surrounding the pipe. As a result of the centrifugal force, a fog formed by the liquid is produced at the outer edge of the disk, and the solid particles are guided through this fog before they are spun off to the outside. During this process, the particles are covered by a layer of the liquid, which is then cooled so as to solidify.
The known device does not provide the possibility to heat the turbine to a controlled temperature. However, as it may be important under certain circumstances to heat the melt to an exactly controlled temperature before it emerges from the draw gap, because its viscosity characteristics can be influenced in this way, it is not always easy with the known devices to adhere to and maintain the desired melt temperature in the turbine.
This situation is aggravated by the fact that in the case of the known device the turbine rotates in a housing which also accommodates the turbine shaft bearings. There exists a gap between the housing and the rotating turbine extends into the bearing space. The packing provided in this gap does not in all cases suffice to prevent any product, especially such of a liquid nature, that may collect at the edge of the housing, radially outside the turbine, from settling down.